Experimental analysis of the through-thickness compression properties of z-pinned sandwich composites

• Published in: Composites. Part A, Applied science and manufacturing Applied science and manufacturing, 2011-11, Vol.42 (11), p.1673-1680
• Main Authors: Nanayakkara, A., Feih, S., Mouritz, A.P.
• Format: Article
• Language: English
• Subjects: A. 3-Dimensional reinforcement; A. Polymer-matrix composites (PMCs); acoustics; Applied sciences; B. Mechanical properties; composite materials; Compressing; Compressive properties; Compressive strength; computed tomography; crushing; D. Acoustic emission; Damage; energy; Exact sciences and technology; Forms of application and semi-finished materials; Laminates; Modelling; monitoring; Polymer industry, paints, wood; Splitting; Strengthening; Stresses; Technology of polymers
• ISSN: 1359-835X; 1878-5840
• DOI: 10.1016/j.compositesa.2011.07.020

This paper presents an experimental investigation into the flat-wise compression properties, strengthening mechanisms and failure modes of sandwich composite materials reinforced with orthogonal z-pins. The compression modulus of the sandwich composite increases rapidly with the volume content of z-pins due to their high longitudinal stiffness, however acoustic emission monitoring and X-ray computed tomography reveal that some z-pins are damaged during elastic loading. The compression stress to induce core crushing is increased greatly by z-pinning (up to nearly 700%), although a large percentage of the z-pins fail close to the elastic stress limit by longitudinal splitting and/or kinking. The total absorbed compressive strain energy of the sandwich composite is also improved greatly by z-pinning (more than 600%) due to the z-pins resisting core crushing, even though they are severely damaged. The results and observations presented in this paper have implications on the mechanical modelling of sandwich materials reinforced with brittle z-pins.